Flotation enhancement of low-grade bauxite using oxalic acid as surface pretreatment agent

The proposed mechanism model for oxalic acid pretreatment of diaspore and kaolinite surfaces. • Oxalic acid was first introduced to pretreat the diasporic bauxite. • Surface pretreatment increased the flotation of diaspore from bauxite. • Oxalic acid exposed and increased the Al O bonds on diaspore surface. • Oxalic acid dissolved more Al on kaolinite surface than diaspore. Surface pretreatment on minerals prior to flotation was proved to increase the selectivity of separation process. Organic acid pretreatment of low-grade diasporic-bauxite was conducted, and the effects of oxalic acid on bauxite flotation were investigated in this work. The oxalic acid pretreatment mechanisms were studied by adsorption measurements, zeta potential testing, XPS analysis, and ICP analysis. The flotation results showed that the oxalic acid treatment could significantly improve Al 2 O 3 recovery from 75.39% to 81.88% and decrease SiO 2 recovery from 53.26% to 47.30%. The adsorption capacity of diaspore for sodium oleate (NaOL) increased by 8.50%, while that of kaolinite decreased by 11.72%. XPS analysis revealed that oxalic acid treatment improved the relative contents of unsaturated Al at diaspore surface beneficial to the adsorption of NaOL. While the relative content of Al at kaolinite surface was decreased due to the Al dissolution revealed by ICP results. Zeta potential analysis indicated that oxalic acid changed the surface property of minerals favorable for the selective adsorption of NaOL on diaspore surface rather than kaolinite surface. These findings provided a promising direction for surface pretreatment of low-grade bauxite using oxalic acid for the improvement of the flotation desilication.